This invention relates to a method and device for controlling the sterilization of products in an autoclave.
The technical sector of the invention is the domain for controlling the sterilization cycles performed in devices, in particular, closed, pre-evacuation- and sterilizing gas-type instruments, in order to verify if the sterilization cycle is performed under the correct conditions.
This invention, in particular but not exclusively, is designed to be used in pre-evacuation devices for sterilization by water vapor such as the autoclaves ensuring the sterilization of medical and hospital equipment and for which it is even more necessary to know whether they have been effectively and correctly sterilized, such as, for example, by exposure to water vapor at 134° Celsius for 18 minutes. And these conditions must be satisfied even inside the containers in which this equipment is placed and that are designed to preserve the sterile status of the latter until they are used after they are removed from the autoclave.
These containers are therefore designed, on the one hand, to prevent the penetration of any liquids or other contaminants during storage and transport to the location in which they are opened in order to use the products that they contain, and, on the other, to be sufficiently unsealed to allow vacuum and entry of liquid, such as vapor, for sterilization using pressure differentials created by the pre-vacuum of the container during the sterilization cycle in the autoclave: this is obtained either by exhaust valve systems that open in one direction and another when the external pressure in the container is sufficiently different from the internal pressure in order to allow the vacuum in one direction, and in the other, allow the input of the sterilization liquid such as vapor, or by reducing the communication openings between their internal and external volume, and protecting these openings either mechanically or by various filters such as paper filters that close them, these various elements allow qualifying the internal volume of these containers as “confined” and complement the unsealed characteristic.
As an example, this “unsealed” and confinement characteristic will be defined by a passage section surface value authorized by these filters with respect to the internal volume of the containers equal to at least 0.1% M−1, and preferably 0.5% M−1 and possibly more, but still remaining very low, in order to allow the vacuum, then the input of sterilization vapor liquid within a reasonable amount of time that is compatible with the total duration of a sterilization cycle.
Currently, this type of control of the “correct” sterilization of products contained in a container (that is, for example, that their temperature has been maintained between 121 and 134° Celsius for 3 to 25 minutes, and/or that the pressure variation according to the temperature has correctly followed the equilibrium curve of saturating vapor, called the Regnault curve) can only be performed upon opening the container in order to use the equipment placed inside it, that are supposed to have been correctly sterilized: for this purpose, one places, before their closure and introduction into the autoclave, inside each container, either a sufficiently large and loaded equipment capable of continuously measuring and recording the temperature and pressure or a vapor reactive physiochemical ink indicator, which is checked at the time of opening.
This check is nevertheless pushed back for a long time after sterilization, so that the container may be moved to the location of its use that may be far away from the autoclave; thus in cases of non-compliance, the equipment cannot be used, and it must therefore be sent for re-sterilization, which wastes time and requires the availability of significant advance stock of equipment that have undergone the sterilization cycle and are waiting to be used in order to make up for the risk of the incorrect sterilization of some of them.
The problem presented is therefore to be able to control this at the earliest time possible, either before or right after the containers are removed from the autoclave, even if it is well in advance of using the equipment that they contain, while subsequently preserving the sterilization of the latter until it is used, without needing to use a product and/or a complicated, time-consuming and/or costly method; and this control must be able to be done with all existing unsealed and confined containers, in particular those that are completely made of metal without special adjustments such as a transparent window, as described in the German utility model DE 29802948.